Several aspects of phagocyte biology have been studied using neutrophils (PMN) and monocytes from normal subjects and patients with defective phagocye chemotaxis, degranulation and oxidative metabolism. Studies of the myelopoiesis and timing of Lyonization were performed using females heterozygote for chronic granulomatous disease. The data indicate neutrophil myelopoiesis is by a polyclonal system and that Lyonization occurs at about the ninth myeloid cell division. In other studies of intracellular pools of PMN receptors evidence was obtained indicating that the intracellular pool of C3bi receptors cosediments with specific granules on sucrose gradients. Like our previous studies with the fmet-leu-phe receptors, the C3bi receptors get translocated to the plasma membrane with cell activation. A patient lacking the C3bi receptor was shown to have severe defects of neutrophil adherence and aggregation. EB virus transformed B cells were shown to produce superoxide in response to phorbol myristate acetate making it possible to store normal or patient cells with this capacity. Further studies of neutrophil degranulation resulted in the deveopment of a new cell free model to study granule fusion with the inside of the plasma membrane. Monoclonal antibodies that recognize the inside, but not the outside of the plasma membrane have been made. In other investigations a new technique was developed for purification of normal eosinophils. This technique, which employs differential responsiveness of eosinophils and neutrophils to fmet-leu-phe, makes it possible to obtain 95-100% pure eosinophils from normal subjects. Studies of immunoglobulins from patients with the Hyperimmunoglobulin E-Recurrent Infection (Job's) syndrome indicate a deficiency of antistaphylococcal IgA in this disease. This helps explain the propensity of these patients to staphylococcal infection.